U.S. patent number 5,089,729 [Application Number 07/669,699] was granted by the patent office on 1992-02-18 for power tool with brush shifting and reversing switch assembly.
This patent grant is currently assigned to Black & Decker Inc.. Invention is credited to Robert G. Moores, Jr..
United States Patent |
5,089,729 |
Moores, Jr. |
February 18, 1992 |
Power tool with brush shifting and reversing switch assembly
Abstract
A portable, reversibly driven power tool (11) comprises a
reversible motor and an assembly (17) for electrically switching
the direction of motor rotation and/or for shifting the commutator
brushes (99, 101) for optimizing motor performance in both the
forward and reverse directions. Assembly (17) includes a reversing
switch (56) and an actuator (19) which is movable between forward
and reverse positions for reversing the connections of the
reversing switch (56) to reverse the direction of motor rotation.
Actuator (19) includes (a) a sleeve (81) connected to the reversing
(56) switch and surrounding the motor stator (43) to guide movement
of the actuator (19) between the forward and reverse positions and
(b) a manual control tab (85) ergonomically located in the motor
housing (23) slightly forward of a manual power switch (21) in the
tool handle (35). The commutator brushes (99, 101) and the
rotatable contacts (61, 63) for the reversing switch (56) are
preferably supported on a common support (67 ) and are movable
thereon responsive to the movement of the actuator (19) between the
forward and reverse positions. Assembly (17) provides a strong,
compact construction for electrically switching the direction of
motor rotation and/or shifting of commutator brushes (99, 101), an
ergonomically preferred remote manual actuator tab (85), easy
assembly and a reliable construction.
Inventors: |
Moores, Jr.; Robert G.
(Reisterstown, MD) |
Assignee: |
Black & Decker Inc.
(Newark, DE)
|
Family
ID: |
24687361 |
Appl.
No.: |
07/669,699 |
Filed: |
March 14, 1991 |
Current U.S.
Class: |
310/50; 200/1V;
310/47 |
Current CPC
Class: |
H01H
9/063 (20130101); H02K 23/66 (20130101); H02K
23/18 (20130101) |
Current International
Class: |
H01H
9/02 (20060101); H01H 9/06 (20060101); H02K
23/18 (20060101); H02K 23/66 (20060101); H02K
23/02 (20060101); H02K 007/14 (); H01H
009/26 () |
Field of
Search: |
;310/50,46,47,67R,238,239 ;200/1V,43.17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
0329249 |
|
Aug 1989 |
|
EP |
|
0408986 |
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Jul 1990 |
|
EP |
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4004464 |
|
Jan 1991 |
|
DE |
|
2209885 |
|
May 1989 |
|
GB |
|
Primary Examiner: Stephan; Steven L.
Assistant Examiner: Nguyen; Matthew
Attorney, Agent or Firm: Dearing; Dennis A. Del Ponti; John
D. Yocum; Charles E.
Claims
I claim:
1. A power tool comprising:
a housing having front and rear ends;
a reversible motor in the housing having (a) a stator and (b) an
armature rotatable about an axis and having an output shaft and
commutator at forward and rearward ends of the armature,
respectively;
a reversing switch for reversing the direction of rotation of the
armature;
said reversing switch surrounding the commutator and comprising a
pair of fixed contacts connected to the stator and a pair of
rotatable contacts connectable to the armature;
a manual switch for energizing the motor, said manual switch
extending from the housing;
an actuator connected to the rotatable contacts and movable between
first and second positions for reversing the direction of rotation
of the armature; and
said actuator comprising:
(a) a sleeve spaced forwardly from the commutator, piloted on and
surrounding the stator and rotatable about the armature axis, said
sleeve guiding movement of the actuator between the first and
second position; and
(b) a manually engagable tab extending from the sleeve forwardly of
and remote from the reversing switch, said tab movable between
first and second locations corresponding to first and second
actuator positions.
2. The tool of claim 1 further wherein:
said housing comprises an annular channel coaxial of the armature
axis for receiving and guiding movement of the sleeve.
3. The tool of claim 1 wherein:
said reversing switch comprises a support for the rotatable
contacts; and
said actuator comprises an arm extending from the sleeve and
engaging the rotatable contact support.
4. The tool of claim 1 further comprising:
the housing comprising:
(1) an elongated motor section having top, bottom, front and rear
walls, and enclosing (a) the motor with the armature axis extending
generally in the direction of elongation of the motor section, (b)
the reversing switch and (c) the actuator, the motor section having
an opening through the bottom wall; and
(2) a handle section extending laterally from the bottom wall of
the motor section and having a front wall and a rear wall, the
handle section having an opening in the front wall adjacent to and
downwardly and rearwardly of the motor section opening;
the manual switch extending through the handle section opening;
the tab extending outwardly from the sleeve through the motor
section opening;
said reversing switch comprising a support for the rotatable
contacts; and
said actuator comprising an arm extending rearwardly from the
sleeve and engaging the rotatable contact support.
5. The tool of claim 1 wherein:
said manual switch comprising a blocking tab for engaging the
reversing switch and blocking movement of the rotatable contacts
when the manual switch is in the closed position.
6. The tool of claim 1 further comprising:
a brush support (a) movable about the armature axis, (b) having a
pair of brushes disposed on the support and engagable with the
armature, (c) engaging the actuator and (d) supporting the
rotatable contacts and brushes for movement responsive to the
movement of the actuator between the first and second
positions.
7. The tool of claim 1 further comprising:
the housing comprising:
an elongated motor section having top, bottom, front and rear
walls, and enclosing (a) the motor with the armature axis extending
generally in the direction of elongation of the motor section, (b)
the reversing switch and (c) the actuator, the motor section having
an opening through the bottom wall; and
a handle section extending laterally from the bottom wall of the
motor section and having a front wall and a rear wall, the handle
section having an opening in the front wall adjacent to and
downwardly and rearwardly of the motor section opening;
the manual switch extending through the handle section opening;
the tab extending outwardly from the sleeve through the motor
section opening;
a pair of brushes mounted on the support and engagable with the
armature;
said support engaging the actuator and supporting the rotatable
contacts and brushes for movement responsive to the movement of the
actuator between the first and second positions.
8. A power tool comprising:
a housing having front and rear ends;
a reversible motor comprising an armature having forward and
rearward ends, an output shaft at the forward end of the armature,
a commutator at the rearward end of the armature and a stator
having a pair of field windings, each winding having first and
second ends;
a manual switch for connecting and disconnecting the first end of
each winding to a power source;
first and second spaced winding contacts fixed to the stator, each
winding contact connected respectively to the second end of each
winding;
a brush support rotatably movable relative to the winding contacts
and having a pair of brushes and first and second brush contacts
connected respectively to the brushes;
the winding contacts and the brush contacts comprising a reversing
switch for reversing the direction of rotation of the motor, the
reversing switch surrounding the commutator;
an actuator connected to the brush support and movable between (a)
a first position wherein the first winding and brush contacts are
connected and the second brush and winding contacts are connected
for rotation of the motor in one direction and (b) a second
position wherein the first winding and second brush contacts are
connected and the second winding and the first brush contacts are
connected for rotation of the motor in the opposite direction;
and
said actuator comprising:
(a) a sleeve spaced forwardly from the commutator, piloted on and
surrounding the stator and rotatable about the armature axis, said
sleeve guiding movement of the actuator between the first and
second positions; and
(b) a manually engagable tab extending from the sleeve forwardly of
and remote from the reversing switch, said tab movable between
first and second locations corresponding to first and second
actuator positions.
9. A power tool comprising:
a reversible motor having (a) a stator and (b) an armature
rotatable about an axis and having a commutator disposed at one end
of the armature;
a brush support adjacent to the commutator, rotatably movable about
the armature axis and having a pair of brushes disposed on the
support and engagable with the commutator;
an actuator connected tot he brush support and rotatable about the
armature axis between first and second positions corresponding to
the forward and reverse directions of rotation of the motor
armature; and
said actuator comprising:
(a) a sleeve spaced forwardly from the commutator, piloted on and
surrounding the stator and rotatable about the armature axis, said
sleeve guiding movement of the actuator between the first and
second positions; and
(b) a manually engagable tab extending from the sleeve forwardly of
and remote from the brush support, said tab movable between first
and second locations corresponding to first and second actuator
positions.
Description
FIELD OF THE INVENTION
The invention relates to portable electric tools having reversible
motors and, more particularly, to improvements in brush shifting
and reversing switch assemblies for such motors.
BACKGROUND OF THE INVENTION
In portable electric tools such as portable drills,
screwdriver/drills and screwdrivers, it is desirable to reverse the
direction of rotation of the motor to facilitate, for example, the
loosening and removal of screws, the removal of a drill bit from a
hole or the removal of a thread cutting tool out of a bore after
cutting a thread in the bore by reverse rotation of the cutting
tool.
One conventional method for reversing universal motors is to
reverse the electrical connection of the brushes and stator
windings. To obtain optimum performance and maximum brush life in a
reversing motor, there must be a compensation mechanism for the
distortion in the magnetic field, called "neutral plane shift" that
results from the interaction of the rotor and stator fluxes. One
such mechanism is the shifting of the brush location about the
armature axis in the direction that is opposite of the direction of
rotation of the armature. Such shifting avoids sparking and
excessive brush and commutator wear. In addition, the sparking will
cause electrical noise to be transmitted into the power source
supplying the electrical energy for the tool.
One such brush shifting and reversing switch assembly is disclosed
in U.S. Pat. No. 4,748,353 in which the brush shifting and
reversing switch mechanisms are combined into a single assembly.
The manual actuator for the mechanism is located on the rear of the
motor housing in the plane of the brushes. Such a location has been
found to be undesirable for two reasons. First, the location of the
manual actuator in this position increases the bulkiness of the
motor housing which is undesirable in many portable power tools.
Secondly, it has been found that users prefer the actuator to be
located just forward of the power (trigger) switch.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a compact,
reliable ergonomically preferred brush shifting and/or reversing
switch assembly.
The present invention is particularly concerned with the provision
of an improved actuator in a brush shifting and/or a reversing
switch assembly for a power tool with a reversible motor.
In accordance with one aspect of the invention, as embodied and
described herein, a power tool comprises a housing, a reversible
motor having a stator and an armature rotatable about an axis. A
reversing switch for reversing the direction of rotation of the
armature comprises a pair of fixed contacts connected to the stator
and a pair of rotatable contacts connectable to the armature. An
actuator is connected to the rotatable contacts and is movable
between a first and second positions for reversing the direction of
rotation of the armature. The actuator comprises a sleeve
surrounding the stator and rotatable about the armature axis.
The housing may comprise an annular channel coaxial of the armature
axis for receiving and guiding movement of the actuator sleeve.
The actuator may comprise an arm extending from the sleeve and
engaging a support for the rotatable contacts.
The actuator may further comprise a tab extending outwardly from
the sleeve through an opening in the housing and movable between
first and second locations corresponding to the first and second
actuator positions, respectively. To provide an ergonomically
preferred position for the actuator tab, preferably the tab extends
through an opening in a bottom wall of a motor section of the
housing. A manual switch extends through an opening in a handle
section of a housing which (opening) is adjacent to and downwardly
and rearwardly of the motor section opening.
To prevent operation of the actuator when the manual power switch
is closed, the power switch may comprise a blocking tab for
engaging the reversing switch and blocking movement of the
rotatable contacts.
In accordance with the preferred embodiment, the brushes for the
motor and the rotatable contacts of the reversing switch are
mounted on a common support which engages the actuator and supports
the rotatable contacts and motor brushes for movement responsive to
the movement of the actuator between the first and second
positions.
In accordance with another aspect of the invention, a power tool
comprises a housing and a reversible motor having a stator and an
armature rotatable about an axis and having a commutator disposed
at one end of the armature. A brush support is rotatably movable
about the armature axis and has a pair of brushes disposed on the
support and engagable with the commutator. An actuator is connected
to the brush support and is rotatable about the armature axis
between first and second positions corresponding to the forward and
reverse directions of rotation of the motor armature. The actuator
comprises a sleeve surrounding the stator and rotatable about the
armature axis. The sleeve guides movement of the actuator between
the first and second positions.
Additional objects and advantages in the invention will be apparent
from the detailed description of the preferred embodiment, the
appended claims and the accompanying drawings or may be learned by
practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings which are incorporated in, and constitute
a part of, this specification illustrate one embodiment of the
invention and together with the description served to explain the
principles of the invention. In the drawings, the same reference
numerals indicate the same parts.
FIG. 1 is a fragmentary side elevational view of a power tool with
a brush shifting and reversing switch assembly in accordance with
the preferred embodiment of the invention.
FIGS. 2A, 2B, and 2C are cross-sectional views taken along line
2--2 of FIG. 1 and illustrate, respectively, the neutral, forward,
and reverse positions of the brush shifting and reversing switch
assembly.
FIGS. 3A, 3B and 3C are a transverse cross-sectional view of the
tool housing and the brush shifting and reversing switch assembly
actuator taken along line 3--3 of FIG. 1 and illustrate,
respectively, the neutral, forward and reverse positions of the
actuator. For clarity, the motor and other components of the brush
shifting and reversing switch assembly have been deleted.
FIGS. 4A, 4B and 4C are a schematic circuit diagram of the
reversing switch for the power tool as shown in FIG. 1 and
illustrate, respectively, the neutral, forward, and reverse
positions of the reversing switch.
FIG. 5A is a rear elevational view of a rotatable support for the
brush shifting and reversing switch assembly shown in FIG. 1.
FIG. 5B is a front elevational view of the rotatable support shown
in FIG. 5A.
FIG. 6A is a rear elevational view of a fixed support of the brush
shifting and reversing switch assembly shown in FIG. 1.
FIG. 6B is a front elevational view of the fixed support shown in
FIG. 6A.
FIG. 7A is a rear elevational view, taken along line 7A--7A of FIG.
7C, of the actuator of the assembly for the power tool of FIG.
1.
FIG. 7B is a cross sectional view of the actuator taken along line
7B--7B in FIG. 7A.
FIG. 7C is a side elevational view taken along line 7C--7C of FIG.
7A.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment is a portable power tool such as a drill,
screwdriver/drill or screwdriver and is used to reversibly drive a
tool bit such as a drill bit or screwdriver bit.
In brief, as shown in FIGS. 1, 4, the power tool 11 comprises a
housing 13, a reversible motor 15, and a brush shifting and
reversing switch assembly 17 for reversing the direction of
rotation of motor 15. Assembly 17 includes a manual actuator 19 for
operation of assembly 17. A trigger switch 21 connects and
disconnects motor 21 to an a.c. or d.c. power source 22 which may
be either a battery or line current.
In accordance with the invention, tool 11 comprises housing 13. As
embodied herein, housing 13 (FIG. 1) has a pistol grip
configuration and comprises an elongated motor section 23 having
top, bottom, front and rear walls 25, 27, 29, 31. Section 23
encloses motor 15 (with an axis of rotation 33 extending generally
in the direction of an elongation of section 23), assembly 17 and
actuator 19. A handle section 35 extends laterally from bottom wall
27 of motor section 23 and has front and rear walls 37, 39.
In accordance with the invention, reversible motor 15 has a stator
43 and an armature 45 rotatable about axis 33. As embodied herein,
motor 15 is preferably a conventional, universal motor. Motor 15
(FIGS. 1, 3) includes a pair of field or stator windings 49, 51, an
armature or output shaft 53 and a commutator 55 at the rear end of
armature 45.
In accordance with the invention herein, tool 11 further comprises
a reversing switch 56 for reversing the direction of rotation of
armature 25. As shown best in FIGS. 2-6, switch 57 comprises a pair
of fixed contacts 57, 59 connected to stator 43 and a pair of
rotatable contacts 61, 63 connectable to armature 45. As embodied
herein, switch 56 further comprises a ring shaped support 65 for
fixed contacts 57, 59 and a ring shaped support 67 for rotatable
contacts 61, 63. Ring 65 is fixed to stator 43 through two pairs of
conventional plug-in connectors 69, 71 and 73, 75 (FIG. 6B).
Connector 69 is connected between the first end of field coil 49
and one side of switch 21. Connector 71 is connected between a
first end of field winding 51 and the other side of trigger switch
21. Connector 73 is connected between a second end of field winding
49 and first fixed winding contact 57. Connector 75 is connected
between a second end of field winding 51 and second fixed winding
contact 59.
Ring 67 is rotatably connected to fixed ring 65 by a pair of
cantilevered spring arms 77, 79 (FIGS. 1, 5B) which extends from
ring 67 and are snap fitted in ring 65. Rings 65, 67 form a
relatively sealed enclosure for contacts 55, 59, 61, 63 to thereby
shield reversing switch 56 from contamination and promote longer
life and reliability of switch 56.
According to the invention, actuator 19 (FIGS. 1, 3, 7) is
connected to the rotatable contacts 61, 63 and is movable between
first (FIGS. 2B, 3B, 4B) and second (FIGS. 2C, 3C, 4C) positions
for reversing the direction of rotation of armature 45. Actuator 19
comprises a sleeve 81 surrounding stator 43 and rotatable about
armature axis 33. Sleeve 61 guides movement of actuator 19 between
the first and second positions. As embodied herein, sleeve 81 is
received in and guided by an annular channel 82 (FIG. 1) formed in
motor section 23 and coaxial of armature axis 33. Channel 82 is
defined by walls 84, 86. To further support and guide movement of
sleeve 81 about axis 33, a plurality of ribs 80 (FIGS. 3, 7A, 7B),
which are formed on the inner wall of sleeve 81, loosely and
slidably engage the outer periphery of stator 43 (FIG. 1). The
first (FIGS. 2B, 3B, 4B) and second (FIGS. 2C, 3C, 4C) positions of
the actuator, correspond to the positions of reversing switch 56
which electrically connect motor 15 for operation in the forward
and reverse directions, respectively.
Actuator 19 (FIGS. 1, 7) further comprises a cantilevered arm 83
rearwardly extending from sleeve 81 and a manually engagable
radially outwardly extending tab 85. Arm 83 engages a U-shaped slot
87 formed on the periphery of rotatable contact support 67. Tab 85
extends outwardly from sleeve 81 through an opening 89 in the
bottom wall 27 of motor section 23. Tab 85 is movable in opening 89
between first (FIG. 3B) and second (FIG. 3C) locations
corresponding to the first (FIG. 2B) and second (FIG. 2C) actuator
positions. As shown in FIG. 1, switch 21 extends through an opening
92 in handle section 35 which is adjacent to and downwardly and
rearwardly of motor section opening 89. As will be apparent, tab 85
is thereby located just forward of trigger switch 21 in an
ergonomically desirable location.
The forward and reverse positions of actuator 19 are defined by a
detent formed between sleeve 81 and motor section 23. The detent is
comprised of a cantilevered resilient finger 88 which has a bump 91
for seating in mating recesses 92 (FIGS. 3B, 3C) formed in the
inner wall of motor section 23.
Manual switch 21 is for energizing motor 15 and includes a trigger
95 which is movable between and open and closed position. To
prevent actuator 19 from being operated to reverse the direction of
motor 15 while energized (commonly known as "plugging"), trigger 95
and rotatable ring 67 of reversing switch 17 are interlocked. As
shown in FIGS. 1,2, the interlock is formed by a blocking tab 93
which extends from trigger 95 radially inwardly toward armature
axis 33 and a projection 97 extending from ring 67 radially outward
from axis 33. When trigger 95 is shifted rearwardly to close switch
21, blocking tab 93 is shifted into the path of movement of
projection 97 preventing ring 67 from being shifted from either the
first position (FIG. 3B) to the second position (FIG. 3C) or from
the second position (FIG. 3C) to the first position (FIG. 3B). As
shown in FIGS. 3A, 3B and 3C, reversing switch 57 has a substantial
amount of travel between the forward and reverse positions to
define an intermediate neutral position. The neutral position is
necessary to provide sufficient separation between forward and
reverse so that switch 17 may be discretely and stably locked in
the forward and reverse positions.
In the preferred embodiment, ring 67 for rotatable contacts 63, 65
also serves as a brush support which (1) is movable about armature
axis 33, (2) has a pair of brushes 99, 101 (FIG. 5A) disposed
thereon and (3) is engagable with the armature commutator 55.
Support 67 thus supports rotatable contacts 61, 63 and brushes 99,
101 for movement responsive to the movement of actuator 19 back and
forth between the first and second positions which correspond
respectively to the forward and reverse directions of rotation of
the motor. Brush 99 is electrically connected to contact 61 via
bias spring 103 (FIG. 5A). Brush 101 is electrically connected to
contact 63 via bias spring 105 (FIG. 5B). In the first (forward)
and the second (reverse) positions, brushes 99, 101 are located at
the optimum position corresponding to the neutral plane of the
magnetic field generated by coils 49, 51 when armature 45 is
rotating. Thus, the required position of brushes 99, 101 for
optimum motor performance will dictate the length of travel
(corresponding to the neutral position in FIGS. 2A) of actuator 19
between the forward and reverse positions.
It will be recognized that while brushes 99, 101 and contacts 61,
63 are preferably mounted on unitary support 67, a separate support
(not shown) may be provided for the contacts 61, 63 and for the
brushes 99, 101.
In operation, initially actuator 19 may be located in the second
position (FIGS. 3C, 4C) which electrically connects motor 15 for
rotation in the reverse direction when trigger switch 21 is closed.
In the second position (FIG. 4C) of actuator 19, fixed (winding)
contact 57 and rotatable (brush) contact 61 are electrically
connected and fixed (winding) contact 59 and rotatable (brush)
contact 63 are electrically connected. Thus, current flows from
power source 22 through switch 21, field winding 49, contact 57,
contact 61, brush 99, commutator 55, brush 101, contact 63, contact
59, field winding 51, and switch 21. Brushes 99, 101 are positioned
at a location corresponding to the neutral plane of the magnetic
field generated by coils 49, 51 when armature 45 is driven in the
reverse direction.
To move actuator 19 from the second to the first position, tab 85
is rotated clockwise in FIG. 3C. The movement of tab 85 is
transmitted to rotatable support 67 through sleeve 81 and arm 83.
Sleeve 81 is piloted on the outer diameter of stator 43 and in
housing channel 82. Arm 83 is connected for rotary motion about
armature axis 33 by engagement in slot 87 formed on the periphery
of support 67. In the first position, contacts 57 and 63 are
electrically connected and contacts 59 and 61 are electrically
connected. Also, brushes 99, 101 are now shifted to a position
corresponding to the neutral plane of the magnetic field generated
by coils 49, 51 when armature 45 is rotated in the reverse
direction. When switch 21 is closed, current flows through coil
winding 49, contact 57, contact 61, brush 99, commutator 55, brush
101, contact 63, contact 59 and field winding 51 for rotation of
motor 19 in the forward direction.
To prevent the "plugging" of motor 15, trigger 95 and rotatable
ring 67 of reversing switch 17 are interlocked (i.e., only when
switch 21 is closed). When trigger 95 is shifted to the rear to
close switch 21, blocking tab 93 is positioned in the path of
projection 97 extending from rotatable ring 67 and prevents
movement of ring 67 from the first to the second position or from
the second position to the first position.
In accordance with features of this invention, a compact, reliable
shifting brush and/or reversing switch assembly with an improved
ergonomic actuator is provided. First, because of the requirement
for compactness, placing the actuator in the plane of the brushes
99, 101 would produce an ergonomically poor design. Users prefer an
actuator location just forward of the power (trigger) switch. It
will thus be appreciated that the assembly is particularly
advantageous because by piloting the actuator on stator 43,
actuator tab may be located in the ergonomically preferred position
in front of trigger 95. Secondly, the assembly provides a compact
strong mechanical linkage between the remotely located actuator tab
85 and the rotatable support 67 for brushes 99, 101 and rotatable
contacts 63, 65 of reversing switch 17. Thirdly, the compact
assembly is particularly advantageous in a pistol grip power tool
in which a small size and easy portability are strongly preferred
design goals. Lastly, the invention provides easy assembly and a
reliable construction.
It will be apparent to those skilled in the art that various
modifications and variations can be made in the power tool
brush/reversing switch assembly of the present invention without
departing from the scope or spirit of the invention. Thus, it is
intended that the present invention cover these modifications and
variations provided they come within the scope of the appended
claims and their equivalents.
* * * * *